Mram

Abstract

An MRAM comprises: a plurality of magnetic memory cells each having a magnetoresistive element; and a magnetic field application section. The magnetic field application section applies an offset adjustment magnetic field in a certain direction to the plurality of magnetic memory cells from outside the plurality of magnetic memory cells. Respective data stored in the plurality of magnetic memory cells become the same when the offset adjustment magnetic field is removed.

1. A magnetic random access memory comprising:
 a plurality of magnetic memory cells each having a magnetoresistive element; and 
 a magnetic field application section configured to apply an offset adjustment magnetic field in a certain direction to said plurality of magnetic memory cells from outside said plurality of magnetic memory cells, 
 wherein respective data stored in said plurality of magnetic memory cells are the same when said offset adjustment magnetic field is removed. 
 
     
     
       2. The magnetic random access memory according to  claim 1 ,
 wherein said magnetic field application section includes a magnetic plate attached on a chip in which said plurality of magnetic memory cells are formed, and 
 wherein said magnetic plate applies said offset adjustment magnetic field to said plurality of magnetic memory cells. 
 
     
     
       3. The magnetic random access memory according to  claim 2 ,
 wherein said magnetic plate is attached on said chip by an adhesive layer whose adhesion force varies with position. 
 
     
     
       4. The magnetic random access memory according to  claim 1 ,
 wherein said magnetic field application section includes a magnetic plate attached on a package provided with a chip in which said plurality of magnetic memory cells are formed, and 
 wherein said magnetic plate applies said offset adjustment magnetic field to said plurality of magnetic memory cells. 
 
     
     
       5. The magnetic random access memory according to  claim 4 ,
 wherein said magnetic plate is attached on said package by an adhesive layer whose adhesion force varies with position. 
 
     
     
       6. The magnetic random access memory according to  claim 1 ,
 wherein said magnetic field application section includes a magnetic layer that is formed on said plurality of magnetic memory cells through an interlayer insulating film, and 
 wherein said magnetic layer applies said offset adjustment magnetic field to said plurality of magnetic memory cells. 
 
     
     
       7. The magnetic random access memory according to  claim 1 ,
 wherein said magnetic field application section includes a plurality of magnetic layers that are respectively formed on said plurality of magnetic memory cells through an interlayer insulating film, and 
 wherein each of said plurality of magnetic layers applies said offset adjustment magnetic field to a corresponding one of said plurality of magnetic memory cells. 
 
     
     
       8. The magnetic random access memory according to  claim 7 ,
 wherein said plurality of magnetic layers include: 
 a first magnetic layer having a first film thickness and formed on a first magnetic memory cell among said plurality of magnetic memory cells; and 
 a second magnetic layer having a second film thickness smaller than said first film thickness and formed on a second magnetic memory cell among said plurality of magnetic memory cells, 
 wherein a thickness of said interlayer insulating film between said first magnetic memory cell and said first magnetic layer is larger than a thickness of said interlayer insulating film between said second magnetic memory cell and said second magnetic layer. 
 
     
     
       9. The magnetic random access memory according to  claim 7 ,
 wherein said plurality of magnetic memory cells are formed on a substrate, and said plurality of magnetic layers are arranged on both a front surface side and a rear surface side of said substrate. 
 
     
     
       10. The magnetic random access memory according to  claim 1 ,
 wherein said magnetoresistive element comprises: 
 a magnetic pinned layer whose magnetization direction is fixed; 
 a magnetic free layer whose magnetization direction is reversible; and 
 a nonmagnetic layer sandwiched between said magnetic pinned layer and said magnetic free layer, 
 wherein a leak magnetic field from said magnetic pinned layer is applied as an offset magnetic field to said magnetic free layer, and said offset magnetic field and said offset adjustment magnetic field are opposite in direction at said magnetic free layer. 
 
     
     
       11. The magnetic random access memory according to  claim 10 ,
 wherein said magnetic pinned layer comprises: 
 a first ferromagnetic film being in contact with said nonmagnetic layer; and 
 a second ferromagnetic film antiferromagnetically coupled to said first ferromagnetic film across a nonmagnetic film, 
 wherein a thickness of said second ferromagnetic film is larger than a thickness of said first ferromagnetic film.